For the sake of clarity, the term “video data” is not limited to data representing any particular type of image content and is intended to include data that is representative of one or more still images, wherein the data are periodically or regularly refreshed.
Holographically generated 2D video images are known to possess significant advantages over their conventionally projected counterparts, especially in terms of definition and efficiency. However, the computational complexity of the current hologram generation algorithms preclude their use in real-time applications. Furthermore, even if the existing algorithms were fast enough, the images generated by them are not of sufficient quality for use in a display application.
Traditionally, hologram generation algorithms may proceed by finding holograms that minimise the mean-squared error (MSE) between the desired image and the image produced (the replay field, or RPF) when the hologram is illuminated with coherent light. The inventors have shown that human subjects consider lower signal and noise variance in the RPF to be far more important in display applications. Using this result, a new algorithm optimised to the psychometrically-determined perceptual measure of image quality has been developed.
Holographically generated images may be formed by light leaving a device exhibiting a phase-modulating effect upon light incident upon the device. Typically the device is a spatial light modulator (SLM) and has a field of addressable phase-modulating elements. In some SLMs the phase-modulating elements are a linear or one-dimensional array of elements; in others a two dimensional array may be provided. For simplicity many SLMs have a regular 2-D array of like, generally square, phase-modulating elements; it is however not necessary for the phase-modulating elements to be alike in size or shape.
In general the phase-modulating elements of SLMs are often referred to as “pixels”, and the elements themselves as “pixellated”. The terms are used interchangeably herein. It is not intended herein, when the term “pixel” is used, that any directly viewable picture content is to be seen on the elements concerned.
An object of some embodiments of the invention is to achieve high quality real-time holographic video projection.
An object of some embodiments of the invention is to provide an algorithm for forming a CGH, which algorithm involves a low number of computationally intensive steps.
An object of some embodiments of the invention is to provide a fast algorithm for forming a CGH, which algorithm can be implemented on relatively unsophisticated hardware, such as is currently commercially available.